Coal ploughs used successfully for many years in underground long wall face workings have pick holders arranged on the plough heads, usually on pick carriers pivotally mounted thereon, and provided with sockets into which the plough picks can be inserted by their shank, which is usually flat-sided. The shanks of plough picks which are known and in common use are matched in its conformation and dimensions to the shape and size of the sockets in which they are inserted, so that the picks are held in the sockets of the pick holders with their shanks in form-fitting engagement. To stop the picks from coming out of their holders in the opposite direction to their insertion direction when the plough is in operation, when the plough performs its working motion in the opposite direction to its cutting direction, it is necessary to provide some means of securing the picks in their sockets. Numerous such means have been proposed, e.g. locking pins, studs, and bolts; retaining keys; collets secured with heavy duty dowel pins or screws, etc. (DE-PS 1291708, DE 2538682 C2, DE 3440448 C2, DE 3531781 C1, DE 3122868 C2, DE 3806363 C2, DE 4105238 C2, DE 4431701 C2).
In the known plough pick systems commonly used in mining for many years, the pick holders are invariably designed so that the picks have to be inserted by their shanks into the sockets from the working or coal face side, and must be removed from the sockets in the pick holders towards that side, after the securing elements have been released, when pick replacement is necessary. Frequently the clearance needed for this operation between the plough, or its picks, and the coal face is available only at the end of a long wall face.
The known plough pick systems commonly used in the mining industry usually require, besides the securing elements used as loose parts, additional fastening elements for fixing the securing elements in the locked position. Such fastening elements include, among others, elastic clamps, plastic plugs provided with steel pins, clamping collets and screws, etc. The result of using such additional fastening elements is that production costs, and consequently plant costs, are increased. In many cases the known systems are difficult to handle when picks are being inserted or replaced, and/or are unreliable in service so that losses of picks while the plough is operating are not uncommon. One known system uses securing elements consisting of captive spring-mounted plunger pins on the pick which automatically snap into the locked position upon insertion of the pick into the holder (DE 4102140 A1). Here again the picks must be inserted into the pick holders from the working side, and removed towards that side.
Taking as its starting-point a plough pick system of the kind initially referred to, the invention has the basic object of providing a pick arrangement, suitable for use in mining, which can be handled more easily when the pick is inserted into the holder, and also when the pick is being removed for replacement.